Communication of information to the public is a major industry. One of the major means of such communications is by publicly visible signs, including advertising signs. Signs have been in use for centuries, and have performed a valuable service of informing consumers about choices that are available to them. But advances in technology have made traditional signs seem somewhat out of date.
U.S. Pat. No. 6,060,993 issued to Eyal Cohen (the “Cohen Patent”) discloses one possible system for displaying messages in advertisements on mobile signs, such as those placed on the tops of motor vehicles such as taxis. In this system a geographic area is divided up into separate zones and when a mobile unit makes a transition from one zone into another the controller located on the mobile unit determines when it has made such a transition based on a positioning system within the mobile unit, on a series of geographic zone definitions which it stores in its memory, and on a schedule indicating which messages are to be shown in which zones at which times. The Cohen patent is hereby incorporated herein by reference in its entirety.